Samsung’s flagship Galaxy S III handset usurped the Apple iPhone 4S as the world’s best-selling smartphone in the third quarter of 2012, according to a new report released by market research and consulting firm Strategy Analytics.

The figures show the S III to have shifted 18 million units in Q3, compared to the iPhone 4S’ 16.2 million. Meanwhile, the S III commanded a 10.7% share of the global smartphone market compared to the iPhone 4S’ 9.7%.

It’s worth noting that sales of the 4S were tempered by the launch of the iPhone 5 in Q3. Apple’s latest handset sold 6 million units and grabbed 3.6% global smartphone market share, Strategy Analytics says.

Samsung’s claim to the smartphone crown is unlikely to be maintained though. The iPhone 5 launched close to the end of the third quarter of the year and suffered limited availability at first.

The S III is still selling healthily, having sold 10 million units in the past two months alone, and has sold more than 30 million units this year, according to Samsung. Still, it won’t be surprising if Q4 sees the now widely available iPhone 5 rise as rapidly as the S III did. In Q2, the Samsung’s flagship sold just 5.4 million units according to Strategy Analytics, so such fast increases are certainly possible. Indeed, Neil Mawston, Executive Director at Strategy Analytics, says in today’s press release, “We expect the new iPhone 5 to out-ship Samsung’s Galaxy S3 in the coming fourth quarter of 2012 and Apple should soon reclaim the title of the world’s most popular smartphone model.”

With Samsung and Apple the undisputed kings of the smartphone market right now, releasing flagship devices once per year, six months apart from each other, it wouldn’t be surprising to see the top spot in studies such as this one flip between the two companies regularly.